Semiconductor device, a method of manufacturing the same and an electronic device

ABSTRACT

The semiconductor device is high in both heat dissipating property and connection reliability in mounting. The semiconductor device includes a semiconductor chip, a resin sealing member for sealing the semiconductor chip, a first conductive member connected to a first electrode formed on a first main surface of the semiconductor chip, and a second conductive member connected to a second electrode formed on a second main surface opposite to the first main surface of the semiconductor chip, the first conductive member being exposed from a first main surface of the resin sealing member, and the second conductive member being exposed from a second main surface opposite to the first main surface of the resin sealing member and also from side faces of the resin sealing member.

CROSS-REFERENCES

This is a continuation application of U.S. Ser. No. 12/759,008, filed Apr. 13, 2010, which is a continuation application of U.S. Ser. No. 12/155,479, filed Jun. 5, 2008 (now U.S. Pat. No. 7,728,416), which is a continuation application of U.S. Ser. No. 11/131,367, filed May 18, 2005 (now abandoned), which is a divisional application of U.S. Ser. No. 10/755,375, filed Jan. 13, 2004 (now U.S. Pat. No. 6,992,385). The entire disclosures of all of the above-identified applications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a packaging technique for a semiconductor device.

As one of semiconductor devices there is known a power transistor used as a switching element in, for example, a power amplifier circuit or a power supply circuit. As to the power transistor, there have been proposed various structures, which have been produced on a commercial basis. For example, in Japanese Published Unexamined Patent Application No. 2000-223634 (Patent Literature 1) there is disclosed a surface-mounted type power transistor. In the same publication (FIG. 17 and paragraphs [0058] and [0059] in the specification) there also is disclosed a technique wherein a portion of lead terminals bonded to electrodes on a main surface of a semiconductor chip are exposed from an upper surface of a resin housing to decrease the heat resistance of a semiconductor package.

[Patent Literature 1]

-   Japanese Published Unexamined Patent Application No. 2000-223634

SUMMARY OF THE INVENTION

In the power transistor, since the amount of an electric current handled therein is large, it is desired to provide a package structure which is superior in heat dissipating property for releasing heat from a semiconductor chip to the exterior and which is low in cost and high in reliability.

In order to obtain a package structure low in cost and high in reliability, it is effective to seal a semiconductor chip with resin. In this case, however, the heat dissipating property is deteriorated because the resin is low in thermal conductivity.

In a package wherein a semiconductor chip is sealed with resin, it is effective to adopt such a both upper-/lower-surface heat dissipating structure as is disclosed in the foregoing Patent Literature 1 wherein a portion of lead terminals connected to electrodes on a main surface of a semiconductor chip are exposed from an upper surface of a resin housing, and die terminals connected to electrodes on a back side opposite to the main surface of the semiconductor chip are exposed from a lower surface opposite to the upper surface of the resin housing.

In the both upper-/lower-surface heat dissipating structure disclosed in the Patent Literature 1, however, since die terminals are not exposed from side faces of the resin housing, it is difficult to form solder fillet which is necessary for improving the connection reliability in soldering at the time of packaging. It is also difficult to judge whether soldering is good or bad by visual inspection.

Besides, since the lead terminals do not have any portion positioned in the interior of the resin housing and the entire upper surface of each lead terminal is exposed from the resin housing, the lead terminals are apt to come off from the resin housing, thus resulting in deterioration of reliability.

It is an object of the present invention to provide a novel semiconductor device high in heat dissipating property and also high in connection reliability in packaging.

It is another object of the present invention to provide a novel semiconductor device high in heat dissipating property and able to judge whether soldering is good or bad by visual inspection at the time of packaging.

It is a further object of the present invention to provide a novel semiconductor device high in both heat dissipating property and reliability.

It is still further object of the present invention to provide a novel semiconductor device high in heat dissipating property.

It is a still further object of the present invention to provide an electronic device high in heat dissipating property.

The above and other objects and novel features of the present invention will become apparent from the following description and the accompanying drawings.

Typical modes of the present invention as disclosed herein will be outlined below.

(1) A semiconductor device comprises:

-   a semiconductor chip having first and second main surfaces     positioned on mutually opposite sides, a first electrode formed over     the first main surface, and a second electrode formed over the     second main surface; -   a resin sealing member sealing the semiconductor chip, and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member, in which one end side is positioned over     the first electrode of the semiconductor chip and connected to the     first electrode of the semiconductor chip through a connecting     means, and the other end side opposite to the one end side is     positioned on the second main surface side of the resin sealing     member relative to the one end side and exposed from the resin     sealing member; and -   a second conductive member connected to the second electrode of the     semiconductor chip through a second connecting means, -   wherein the one end side of the first conductive member is exposed     from the first main surface of the resin sealing member, and the     second conductive member is exposed from the second main surface and     side faces of the resin sealing member.     (2) In the semiconductor device of the above (1), the other end side     of the first conductive member is positioned on a first side-face     side of the resin sealing member, and the second conductive member     is exposed from a second side face opposite to the first side face     of the resin sealing member.     (3) In the semiconductor device of the above (1), the first     electrode of the semiconductor chip is a source electrode and the     second electrode of the semiconductor chip is a drain electrode, or     the first electrode of the semiconductor chip is a drain electrode     and the second electrode of the semiconductor chip is a source     electrode.     (4) A semiconductor device comprises: -   a semiconductor chip having first and second main surfaces     positioned on mutually opposite sides, a first electrode formed over     the first main surface, and a second electrode formed over the     second main surface; -   a resin sealing member sealing the semiconductor chip and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member having a first portion, a second portion,     and a third portion, the first portion being positioned over the     first electrode of the semiconductor chip, connected to the first     electrode of the semiconductor chip through a first connecting means     and exposed from the first main surface of the resin sealing member,     the second portion being formed integrally with the first portion     and positioned in the interior of the resin sealing member, and the     third portion being formed integrally with the second portion and     exposed from the second main surface of the resin sealing member;     and -   a second conductive member connected to the second electrode of the     semiconductor chip through a second connecting means and exposed     from the second main surface of the resin sealing member.     (5) In the semiconductor device of the above (4), the third portion     of the first conductive member is exposed from a first side face of     the resin sealing member, and the second conductive member is     exposed from a second side face opposite to the first side face of     the resin sealing member.     (6) In the semiconductor device of the above (4), the first     electrode of the semiconductor chip is a drain electrode and the     second electrode of the semiconductor chip is a source electrode.     (7) A semiconductor comprises: -   a semiconductor chip, the semiconductor chip having first and second     main surfaces positioned on mutually opposite sides, first and     second electrodes formed over the first main surface, and a third     electrode formed over the second main surface; -   a resin sealing member sealing the semiconductor chip and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member having a first portion, a second portion,     and a third portion, the first portion being connected to the first     electrode of the semiconductor chip through a first connecting     means, the second portion being formed integrally with the first     portion, and the third portion being formed integrally with the     second portion and positioned on the second main surface side of the     resin sealing member relative to the first portion; -   a second conductive member having a first portion, a second portion,     and a third portion, the first portion being connected to the second     electrode of the semiconductor chip through a second connecting     means, the second portion being formed integrally with the first     portion, and the third portion being formed integrally with the     second portion and positioned on the second main surface side of the     resin sealing member relative to the first portion; and -   a third conductive member connected to the third electrode of the     semiconductor chip through a third connecting means and exposed from     the second main surface of the resin sealing member, -   wherein the first portion of the first conductive member is exposed     from the first main surface of the resin sealing member, and the     first portion of the second conductive member is positioned in the     interior of the resin sealing member.     (8) In the semiconductor device of the above (7), the first portion     of the second conductive member is smaller in thickness than the     first portion of the first conductive member of the first conductive     member.     (9) In the semiconductor device of the above (7), the second     portions of the first and second conductive members are positioned     in the interior of the resin sealing member, and the third portions     of the first and second conductive members are exposed from the     second main surface of the resin sealing member.     (10) In the semiconductor device of the above (7), the third     portions of the first and second conductive members are exposed from     a first side face of the resin sealing member, and the third     conductive member is exposed from a second side face opposed to the     first side face of the resin sealing member.     (11) In the semiconductor device of the above (7), the first     electrode of the semiconductor chip is a source electrode, the     second electrode of the semiconductor chip is a gate electrode, and     the third electrode of the semiconductor chip is a drain electrode.     Alternatively, the first electrode of the semiconductor chip is a     drain electrode, the second electrode of the semiconductor chip is a     gate electrode, and the third electrode of the semiconductor chip is     a source electrode.     (12) A semiconductor device comprises: -   a semiconductor chip having first and second main surfaces     positioned on mutually opposite sides, first and second electrodes     formed over the first main surface, and a third electrode formed     over the second main surface; -   a resin sealing member sealing the semiconductor chip and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member having a first portion, a second portion,     and a third portion, the first portion being connected to the first     electrode of the semiconductor chip through a first connecting     means, the second portion being formed integrally with the first     portion, and the third portion being positioned on the second main     surface side of the resin sealing member relative to the first     portion; -   a second conductive member positioned outside the semiconductor chip     and on the second main surface side of the resin sealing member     relative to the first portion of the first conductive member; and -   a third conductive member connected to the third electrode of the     semiconductor chip through a second connecting means and exposed     from the second main surface of the resin sealing member, -   wherein the first portion of the first conductive member is exposed     from the first main surface of the resin sealing member, and the     second conductive member is connected electrically to the second     electrode of the semiconductor chip through a bonding wire.     (13) In the semiconductor device of the above (12), the second     portion of the first conductive member is positioned in the interior     of the resin sealing member, and the third portion of the first     conductive member and the second conductive member are exposed from     the second main surface of the resin sealing member.     (14) A semiconductor device comprises: -   a semiconductor chip having first and second main surfaces     positioned on mutually opposite sides, a first electrode formed over     the first main surface, and a second electrode formed over the     second main surface; -   a resin sealing member sealing the semiconductor chip, and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member having a first portion, a second portion,     and a third portion, the first portion being connected to the first     electrode of the semiconductor chip through a first connecting     means, the second portion being formed integrally with the first     portion, and the third portion being formed integrally with the     second portion and positioned on the second main surface side of the     resin sealing member relative to the first portion; and -   a second conductive member having a first portion connected to the     second electrode of the semiconductor chip through a second     connecting means and a second portion formed integrally with the     first portion and larger in thickness than the first portion, -   wherein the first portion of the second conductive member is exposed     from the second main surface of the resin sealing member, and the     second portion of the second conductive member is exposed from the     first and second main surfaces of the resin sealing member.     (15) In the semiconductor device of the above (14), the second     portion of the second conductive member is exposed from side faces     of the resin sealing member.     (16) In the semiconductor device of the above (14), the first     electrode of the semiconductor chip is a source electrode and the     second electrode of the semiconductor chip is a drain electrode.     Alternatively, the first electrode of the semiconductor chip is a     drain electrode and the second electrode of the semiconductor chip     is a source electrode.     (17) A semiconductor device comprises: -   a semiconductor chip having first and second main surfaces     positioned on mutually opposite sides, a first electrode formed over     the first main surface, and a second electrode formed over the     second main surface; -   a resin sealing member sealing the semiconductor chip and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member having a first portion connected to the     first electrode of the semiconductor chip through a first connecting     means and a second portion formed integrally with the first portion     and smaller in thickness than the first portion; and -   a second conductive member having a first portion connected to the     second electrode of the semiconductor chip through a second     connecting means and a second portion formed integrally with the     first portion and larger in thickness than the first portion, -   wherein the first and second portions of the first conductive member     are exposed from the first main surface of the resin sealing member,     the second portion of the first conductive member is exposed from     the second main surface of the resin sealing member, the first     portion of the second conductive member is positioned in the     interior of the resin sealing member, and the second portion of the     second conductive member is exposed from the second main surface of     the resin sealing member.     (18) In the semiconductor device of the above (17), the second     portion of the first conductive member is exposed from side faces of     the resin sealing member.     (19) In the semiconductor device of the above (17), the first     electrode of the semiconductor chip is a drain electrode and the     second electrode of the semiconductor chip is a source electrode.     Alternatively, the first electrode of the semiconductor chip is a     source electrode and the second electrode of the semiconductor chip     is a drain electrode.     (20) An electronic device comprises a wiring substrate, a     semiconductor device mounted over the wiring substrate, and a heat     dissipating member disposed over the semiconductor device, -   the semiconductor device comprising: -   a semiconductor chip having first and second main surfaces     positioned on mutually opposite sides, first and second electrodes     formed over the first main surface, and a third electrode formed     over the second main surface; -   a resin sealing member sealing the semiconductor chip and having     first and second main surfaces positioned on mutually opposite     sides, the first main surface being positioned on the first main     surface side of the semiconductor chip, and the second main surface     being positioned on the second main surface side of the     semiconductor chip; -   a first conductive member having a first portion, a second portion,     and a third portion, the first portion being connected to the first     electrode of the semiconductor chip through the first connecting     means and exposed from the first main surface of the resin sealing     member, the second portion being formed integrally with the first     portion, and the third portion being formed integrally with the     second portion and exposed from the second main surface of the resin     sealing member; -   a second conductive member having a first portion, a second portion,     and a third portion, the first portion being connected to the second     electrode of the semiconductor chip through a second connecting     means and positioned in the interior of the resin sealing member,     the second portion being formed integrally with the first portion,     and the third portion being exposed from the second main surface of     the resin sealing member; and -   a third conductive member connected to the third electrode of the     semiconductor chip through a third connecting means and exposed from     the second main surface of the resin sealing member, -   wherein the third portions of the first and second conductive     members, as well as the third conductive member, are soldered to     electrodes formed over the wiring substrate, and the first portion     of the first conductive member is connected to the heat dissipating     member through a heat conducting member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view (top view) showing an appearance of a power transistor according to a first embodiment of the present invention;

FIG. 2 is a bottom view (underside view) showing an appearance of the power transistor (semiconductor device) of the first embodiment;

FIG. 3 is a plan view showing an internal structure of the power transistor of the first embodiment;

FIG. 4 is an enlarged sectional view taken along line a-a in FIG. 3;

FIG. 5 is an enlarged sectional view taken along line b-b in FIG. 3;

FIGS. 6( a) and 6(b) illustrate a schematic construction of a regulator (electronic device) with the power transistor incorporated therein, in which FIG. 6( a) is a plan view and FIG. 6( b) is a sectional view taken along line a-a in FIG. 6( a);

FIG. 7 is a partially enlarged sectional view of FIG. 6( b);

FIG. 8 is an enlarged sectional view taken along line b-b in FIG. 6( a);

FIG. 9 is an equivalent circuit diagram showing a schematic construction of the regulator of FIG. 6;

FIG. 10 is a plan view showing a part of a lead frame used in manufacturing the power transistor of the first embodiment;

FIGS. 11( a) and 11(b) are partially enlarged views of the lead frame of FIG. 10, in which FIG. 11( a) is a plan view and FIG. 11( b) is a sectional view taken along line a-a in FIG. 11( a);

FIG. 12 is a plan view of a header used in manufacturing the power transistor of the first embodiment;

FIG. 13 is a sectional view of a semiconductor chip used in manufacturing the power transistor of the first embodiment;

FIG. 14 is a bottom view (underside view) of the semiconductor chip shown in FIG. 13;

FIG. 15 is a plan view of a semiconductor wafer used in manufacturing the power transistor of the first embodiment;

FIGS. 16( a) to 16(d) illustrate dicing steps for dicing the semiconductor wafer into individual semiconductor chips in manufacturing the power transistor of the first embodiment, in which FIGS. 16( a) to 16(d) are sectional views;

FIGS. 17( a) and 17(b) illustrate a manufacturing step in manufacturing the power transistor of the first embodiment, in which FIG. 17( a) is a plan view and FIG. 17( b) is a sectional view taken along line a-a in FIG. 17( a);

FIGS. 18( a) and 18(b) illustrate a manufacturing step in manufacturing the power transistor of the first embodiment, in which FIG. 18( a) is a plan view and FIG. 18( b) is a sectional view taken along line a-a in FIG. 18( a);

FIG. 19 is a partially enlarged sectional view of FIG. 18( b);

FIG. 20 is a plan view illustrating a manufacturing step in manufacturing the power transistor of the first embodiment;

FIGS. 21( a) and 21(b) illustrate a manufacturing step in manufacturing the power transistor of the first embodiment, in which FIG. 21( a) is a sectional view taken at a position corresponding to line a-a in FIG. 20 and FIG. 21( b) is a sectional view taken at a position corresponding to line b-b in FIG. 20;

FIGS. 22( a) and 22(b) illustrate a manufacturing step in manufacturing the power transistor of the first embodiment, in which FIG. 22( a) is a sectional view taken at a position corresponding to line a-a in FIG. 20 and FIG. 22( b) is a sectional view taken at a position corresponding to line b-b in FIG. 20;

FIG. 23 is a plan view illustrating a manufacturing step in manufacturing the power transistor of the first embodiment;

FIGS. 24( a) and 24(b) illustrate a manufacturing step in manufacturing the power transistor of the first embodiment, in which FIG. 24( a) is a plan view and FIG. 24( b) is a sectional view taken along line a-a in FIG. 24( a);

FIG. 25 is a sectional view of a principal portion, showing a schematic construction of a regulator according to a first modification of the first embodiment;

FIGS. 26( a) and 26(b) illustrate an internal structure of a power transistor according to a second modification of the first embodiment, in which FIG. 26( a) is a plan view and FIG. 26( b) is a sectional view taken along line a-a in FIG. 26( a);

FIGS. 27( a) and 27(b) illustrate an internal structure of a power transistor according to a third modification of the first embodiment, in which FIG. 27( a) is a plan view and FIG. 27( b) is a sectional view taken along a-a in FIG. 27( a);

FIGS. 28( a) and 28(b) illustrate an internal structure of a power transistor according to a fourth modification of the first embodiment, in which FIG. 28( a) is a plan view and FIG. 28( b) is a sectional view taken along line a-a in FIG. 28( a);

FIGS. 29( a) and 29(b) illustrates an internal structure of a power transistor according to a fifth modification of the first embodiment, in which FIG. 29( a) is a plan view and FIG. 29( b) is a sectional view taken along line a-a in FIG. 29( a);

FIG. 30 is a plan view illustrating an internal structure of a power transistor according to a sixth modification of the first embodiment;

FIG. 31 is a sectional view illustrating an internal structure of a power transistor according to a seventh modification of the first embodiment;

FIGS. 32( a) and 32(b) illustrate appearance of a power transistor according to a second embodiment of the present invention, in which FIG. 32( a) is a plan view (top view) and FIG. 32( b) is a bottom view (underside view);

FIG. 33 is a sectional view taken along line a-a in FIG. 32( a);

FIG. 34 is a plan view (top view) showing an appearance of a power transistor according to a third embodiment of the present invention;

FIG. 35 is a bottom view (underside view) showing an appearance of the power transistor of the third embodiment;

FIG. 36 is an enlarged sectional view taken along line a-a in FIG. 35;

FIG. 37 is an enlarged sectional view taken along line b-b in FIG. 35;

FIG. 38 is a plan view (top view) showing an appearance of a power transistor according to a fourth embodiment of the present invention;

FIG. 39 is a bottom view (underside view) showing an appearance of the power transistor of the fourth embodiment;

FIG. 40 is a plan view showing an internal structure of the power transistor of the fourth embodiment;

FIG. 41 is an enlarged sectional view taken along line a-a in FIG. 40:

FIG. 42 is an enlarged sectional view taken along line b-b in FIG. 40;

FIG. 43 is a plan view showing an internal structure of a power transistor according to a fifth embodiment of the present invention;

FIGS. 44( a) and 44(b) illustrate an internal structure of the power transistor of the fifth embodiment, in which FIG. 44( a) is a sectional view taken along line a-a in FIG. 43 and FIG. 44 (b) is a sectional view taken along line b-b in FIG. 43;

FIG. 45 is a plan view showing an appearance of a power transistor according to a sixth embodiment of the present invention;

FIG. 46 is a bottom view showing an appearance of the power transistor of the sixth embodiment; and

FIGS. 47( a) and 47(b) illustrates an internal structure of the power transistor of the sixth embodiment, in which FIG. 47( a) is a sectional view taken along line a-a in FIG. 45 and FIG. 47( b) is a sectional view taken along line b-b in FIG. 45.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail hereinunder with reference to the accompanying drawings. In all of the drawings for illustrating the embodiments, components having the same functions are identified by the same reference numerals in principle, and repeated explanations thereof will be omitted. Further, for making the drawings easier to see, hatchings which represent sections are partially omitted.

First Embodiment

FIG. 1 is a plan view (top view) showing an appearance of a power transistor according to a first embodiment of the present invention, FIG. 2 is a bottom view (underside view) showing an appearance of the power transistor (semiconductor device) of the first embodiment, FIG. 3 is a plan view showing an internal structure of the power transistor of the first embodiment, FIG. 4 is an enlarged sectional view taken along line a-a in FIG. 3, and FIG. 5 is an enlarged sectional view taken along line b-b in FIG. 3.

As shown in FIGS. 1 to 5, a power transistor 1A according to this first embodiment comprises a semiconductor chip 2, a resin sealing member 11 for sealing the semiconductor chip 2, leads (6, 8) as conductive members, and a header 7.

As shown in FIGS. 3 to 5, the semiconductor chip 2 is quadrangular in a planar shape thereof perpendicular to its thickness direction. Further, the semiconductor chip 2 has a main surface 2 x and a back surface 2 y which are positioned on mutually opposite sides in the thickness direction of the semiconductor chip. On the main surface 2 x are formed a source electrode 3 and a gate electrode 5, while on the back surface 2 y is formed a drain electrode 4.

The semiconductor chip 2 is composed principally of a semiconductor substrate formed of a single crystal silicon for example. On the main surface of the semiconductor substrate there is formed a MISFET (Metal Insulator Semiconductor Field Effect Transistor) of a vertical structure for example. In the vertical MISFET, a plurality of fine transistor cells are connected in parallel in order to obtain a large electric power.

The semiconductor chip 2 is sealed with a resin sealing member 11. As shown in FIGS. 1, 2, and 4, the resin sealing member 11 is quadrangular in a planar shape thereof perpendicular to its thickness direction. Further, the resin sealing member has a main surface (upper surface) 11 x and a back surface (lower surface, mounting surface) 11 y which are positioned on mutually opposite sides in the thickness direction of the semiconductor chip. The main surface 11 x is positioned on the main surface 2 x side of the semiconductor chip 2, while the back surface 11 y is positioned on the back surface 2 y side of the semiconductor chip 2.

For the purpose of reducing a stress, the resin sealing member 11 is formed using, for example, an epoxy-based thermosetting resin with a phenolic curing agent, silicone rubber and filler incorporated therein. The resin sealing member 11 is formed by a transfer molding method which is suitable for mass production. According to the transfer molding method, there is used a molding die provided with pot, runner, resin pouring gate, and cavity, and a thermosetting resin is injected from the pot into the cavity through the runner and the resin pouring gate to form a resin sealing member.

As shown in FIGS. 3 and 4, the lead 6 is formed by bending and has a first portion 6 a, a second portion 6 b, and a third portion 6 c. A part of the first portion 6 a is positioned above the source electrode 3 of the semiconductor chip 2 and another part thereof projects to the outside of the semiconductor chip 2 across a first side out of first and second sides of the main surface 2 x of the semiconductor chip 2 which first and second sides are positioned on mutually opposite sides in a first direction (X direction). The second portion 6 b is formed integrally with the first portion 6 a and is bent from the first portion 6 a toward the back surface 11 y of the resin sealing member 11. The third portion 6 c is formed integrally with the second portion 6 b and extends in the same direction (away from the semiconductor chip 2) as the projecting direction of the first portion 6 a from the second portion 6 b.

The first portion 6 a of the lead 6 is connected electrically and mechanically to the source electrode 3 of the semiconductor chip 2 through, for example, a plurality of salient electrodes 9 as connecting means. The second portion 6 b of the lead 6 is an offset portion for spacing the first portion 6 a and the third portion 6 c from each other. The third portion 6 c of the lead 6 is positioned on the back surface 11 y side of the resin sealing member 11 relative to the first portion 6 a through the second portion 6 b.

As shown in FIGS. 1 and 4, the first portion 6 a of the lead 6 is exposed from the main surface 11 x of the resin sealing member 11. As shown in FIGS. 2 and 3, the third portion 6 c of the lead 6 is exposed from the back surface 11 y of the resin sealing member 11 and is further exposed from a first side face 11 z out of first and second side faces 11 z of the resin sealing member 11 which first and second side faces are positioned on mutually opposite sides in X direction. That is, one end side of the lead 6 is positioned above the source electrode 3 of the semiconductor chip 2, is connected to the source electrode 3 of the semiconductor chip 2 through salient electrodes (connecting means) 9, and is exposed from the main surface 11 x of the resin sealing member 11, while the other end side opposite to the one end side is positioned on the back surface side of the resin sealing member 11 relative to the one end side and is exposed from both back surface 11 y an first side face 11 z of the resin sealing member.

Like the lead 6, the lead 8 is also formed by bending and has a first portion 8 a, a second portion 8 b, and a third portion 8 c. A part of the first portion 8 a is positioned above the gate electrode 5 of the semiconductor chip 2, while another part thereof, like that of the lead 6, projects to the outside of the semiconductor chip 2 across the first side of the main surface 2 x of the semiconductor chip. The second portion 8 b is formed integrally with the first portion 8 a and is bent from the first portion 8 a toward the back surface 11 y of the resin sealing member 11. The third portion 8 c is formed integrally with the second portion 8 b and extends in the same direction (away from the semiconductor chip 2) as the projecting direction of the first portion 8 a from the second portion 8 b.

The first portion 8 a of the lead 8 is connected electrically and mechanically to the gate electrode 5 of the semiconductor chip 2 through, for example, a salient electrode 9 as connecting means. The second portion 8 b of the lead 8 is an offset portion for spacing the first portion 8 a and the third portion 8 c from each other in the thickness direction of the resin sealing member 11. The third portion 8 c of the lead 8 is positioned on the back surface 11 y side of the resin sealing member 11 relative to the first portion 8 a through the second portion 8 b.

As shown in FIGS. 1 and 5, the first portion 8 a of the lead 8 is positioned in the interior of the resin sealing member 11. As shown in FIGS. 2 and 5, the third portion 8 c of the lead 8 is exposed from the back surface 11 y of the resin sealing member 11 and is further exposed, like the lead 6, from the first side face 11 z of the resin sealing member 11. That is, one end side of the lead 8 is positioned above the second gate electrode 5 of the semiconductor chip 2, is connected to the gate electrode 5 of the semiconductor chip 2 through a salient electrode (connecting means) 9, and is positioned in the interior of the resin sealing member 11, while the other end side thereof opposite to the one end side is positioned on the back surface side of the resin sealing member 1 relative to the one end side and is exposed from the back surface 11 y and the first side face 11 z of the resin sealing member 11.

For example, as shown in FIGS. 3 and 4, plural salient electrodes 9 are interposed between and fixed to the source electrode 3 of the semiconductor chip 2 and the first portion 6 a of the lead 6.

For example, as shown in FIGS. 3 and 5, one salient electrode 9 is interposed between and fixed to the gate electrode 5 of the semiconductor chip 2 and the first portion 8 a of the lead 8.

As the salient electrode(s) there is used, for example, a stud bump formed of gold (Au) though there is made no limitation thereto. For example, the stud bump is formed by forming a ball at the tip of Au wire, then thermocompression-bonding the ball to an electrode on the chip under ultrasonic oscillation, and subsequently cutting off the Au wire from the ball. In case of using a stud bump as the salient electrode 9, the electrode-lead connection on the semiconductor chip is performed by thermocompression bonding.

As shown in FIGS. 4 and 5, the header 7 is connected electrically and mechanically to the drain electrode 4 on the back side 2 y of the semiconductor chip 2 through, for example, an electrically conductive adhesive as connecting means. As shown in FIGS. 2, 4, and 5, the header 7 is exposed from the back surface 11 y of the resin sealing member 11 and, as shown in FIGS. 1, 2, 4, and 5, is further exposed from the second side face 11 z opposite to the first side face 11 z of the resin sealing member 11 from which the first portions (6 c, 8 c) of the leads (6, 8) are exposed. In this first embodiment, the header 7 projects from the second side face 11 z of the resin sealing member 11. The third portions (6 c, 8 c) of the leads (6, 8) also project from the first side face 11 z of the resin sealing member 11.

In the header 7, as shown in FIGS. 2 and 5, there is formed a slit 12 extending through an upper surface (chip-connected surface) of the header and further through a lower surface thereof (exposed surface from the resin sealing member). The slit 12 is formed in the other portion than the area where the semiconductor chip 2 is connected, and the interior of the slit 12 is filled with the resin sealing member 11. That is, the slit 12 is provided for preventing dislodgment of the header 7 from the resin sealing member 11.

As shown in FIGS. 1, 4, and 5, the second portions (6 b, 8 b) of the leads 6 and 8 are positioned in the interior of the resin sealing member 11. The thickness 8 at (see FIG. 5) of the first portion 8 a of the lead 8 is larger than the thickness 6 at (see FIG. 4) of the first portion 6 a of the lead 6 so that the first portion 8 a is positioned in the interior of the resin sealing member 11.

As shown in FIG. 3, the width of the lead 6 (the width in the second direction (Y direction) perpendicular to the first direction (X direction) in the same plane) is larger than the width of the lead 8 (the width in the second direction (Y direction) perpendicular to the first direction (X direction) in the same plane). Further, the area of the first portion 6 a of the lead 6 opposed to the main surface 2 x of the semiconductor chip 2 is larger than the area of the first portion 8 a of the lead 8 opposed to the main surface 2 x of the semiconductor chip.

The power transistor 1A thus constructed is soldered, together with other components, onto the wiring substrate in the electronic device. The third portions (6 c, 8 c) of the leads 6 and 8, as well as the header 7, are connected electrically and mechanically to electrodes on the wiring substrate through an electrically conductive adhesive (e.g., a lead-free solder material). That is, the power transistor 1A of this first embodiment is of a surface-mounted type structure wherein the third portion 6 c of the lead 6, the third portion 8 c of the lead 8, and the header 7, which function as external connection terminals soldered at the time of packaging, are arranged on the back surface 11 y of the resin sealing member 11.

As shown in FIGS. 1 to 5, the power transistor 1A is of a both upper-/lower-surface heat dissipating structure wherein the first portion 6 a of the lead 6 is exposed from the main surface 11 x of the resin sealing member 11, and the header 7 is exposed from the back surface 11 y opposite to the main surface 11 x of the resin sealing member 11. With such a structure, heat generated from the semiconductor chip 2 is released to the exterior efficiently from the first portion 6 a of the lead 6 which has a wide area, and is further released to the exterior from the header 7 of a wide area, so that the heat dissipating property of the power transistor 1A is enhanced.

According to the structure of the power transistor 1A, the second portion 6 b of the lead 6 is positioned in the interior of the resin sealing member 11. With such a structure, even if the first portion 6 a of the lead 6 is exposed from the main surface (upper surface) of the resin sealing member 11 for the purpose of improving the heat dissipating property of the power transistor, it is possible to prevent dislodgment of the lead 6 from the resin sealing member 11, so that the reliability of the power transistor 1A is enhanced.

According to the structure of the power transistor 1A, the first portion 6 a of the lead 6 is connected electrically and mechanically to the source electrode 3 of the semiconductor chip 2 through salient electrodes 9, while the first portion 8 a of the lead 8 is connected electrically and mechanically to the gate electrode 5 of the semiconductor chip 2 through a salient electrode 9. With such a structure, a conduction path between the leads and the electrodes on the semiconductor chip becomes shorter and hence the ON resistance of the power transistor 1A becomes lower in comparison with the structure wherein leads and electrodes on a semiconductor chip are connected together electrically through bonding wires. Besides, the thickness of the power transistor 1A can be reduced because the resin thickness of the resin sealing member 11 on the main surface of the semiconductor chip 2 becomes smaller.

According to the structure of the power transistor 1A, the semiconductor chip 2 is resin-sealed with the resin sealing member 11, whereby the reliability of the power transistor 1A is enhanced in comparison with the structure wherein the resin sealing member 2 is not sealed with resin.

Further, according to the structure of the power transistor 1A, the first portion 6 a of the lead 6 is exposed from the main surface 11 x of the resin sealing member 11 and the first portion 8 a of the lead 8 is positioned in the interior of the resin sealing member 11. With such a structure, even in the event an electrically conductive foreign matter should adhere for some reason or other to the main surface 11 x of the resin sealing member 11, it is possible to prevent shorting of the lead 6 with the lead 8 caused by that foreign matter and hence possible to enhance the reliability of the power transistor 1A in comparison with the case where the first portions (6 a, 8 a) of the leads 6 and 8 are exposed from the main surface 11 x of the resin sealing member 11.

FIG. 6 illustrates a schematic construction of a regulator (electronic device) with the power transistor 1A of FIG. 1 incorporated therein, in which FIG. 6( a) is a plan view and FIG. 6 (b) is a sectional view taken along line a-a in FIG. 6( a), FIG. 7 is a partially enlarged sectional view of FIG. 6( b), FIG. 8 is an enlarged sectional view taken along line b-b in FIG. 6( a), and FIG. 9 is an equivalent circuit diagram showing a schematic construction of the regulator of FIG. 6.

As shown in FIG. 9, a regulator 40A is basically provided with a high-side power transistor 1A and a low-side power transistor 1A, in which a DC voltage applied to an input terminal is reduced by voltage conversion and a low DC voltage is outputted from an output terminal. For example, a DC voltage of 12V applied to an input terminal is reduced to a DC voltage of 1.3V, which is outputted from an output terminal. In operation, a current ID1 flows when the high-side power transistor 1A is ON and the low-side power transistor 1A is OFF, while when the high-side power transistor 1A is OFF and the low-side power transistor 1A is ON, there flows a current ID2 by virtue of a counter-electromotive force of coil. ON-OFF of the high- and low-side power transistors 1A is controlled by a control IC. For example, the regulator 40A is used in a power supply section which supplies a server's CPU with a predetermined voltage.

As shown in FIG. 6, the regulator 40A comprises a wiring substrate 41, plural power transistors 1A mounted on the wiring substrate 41, and a heat dissipating member 43 disposed on the plural power transistors 1A so as to cover the power transistors.

The power transistors 1A are mounted on the wiring substrate 41 by soldering for example. As shown in FIG. 8, the first portion 6 a of the lead 6 is connected electrically and mechanically to an electrode 41 a on the wiring substrate 41 through an electrically conductive adhesive (e.g., a lead-free solder material) 42. The first portion 8 a of the lead 8, though not shown, is connected electrically and mechanically to a corresponding electrode on the wiring substrate 41 through the electrically conductive adhesive 42. The header 7 is connected electrically and mechanically to an electrode 41 b on the wiring substrate 41 through the adhesive 42.

Mounting of the power transistor 1A is carried out, for example, by applying a pasty adhesive onto electrodes formed on the wiring substrate by a screen printing method as an example, thereafter disposing the third portion 6 c of the lead 6, the third portion 8 c of the lead 8, and the header 7 onto corresponding electrodes on the wiring substrate 41 through the adhesive, then conveying the wiring substrate 41 into an infrared reflow furnace, and thereafter melting and curing the adhesive, although no limitation is made to this method.

In the mounting step of the power transistors 1A, the third portions (6 c, 8 c) of the leads 6 and 8 are exposed from the first side face 11 z of the resin sealing member 11, so that there is formed a good fillet 42 a having a large thickness of the adhesive 42 in such a manner as to cover side faces of the tips of the third portions (6 c, 8 c). Also as to the header 7, since it is exposed from the second side face 11 z of the resin sealing member 11, there is formed a good fillet 42 a having a large thickness of the adhesive 42 in such a manner as to cover side faces of the header 7 exposed from the second side face 11 z of the resin sealing member.

Thus, by allowing the third portions (6 c, 8 c) of the leads 6 and 8 to be exposed from the first side face 11 z of the resin sealing member 11 and allowing the header 7 to be exposed from the second side face 11 z of the resin sealing member, a good fillet 42 is formed on side faces of the tips of the third portions (6 c, 8 c) of the leads 6 and 8 and also on side faces of the header 7 exposed from the second side face 11 z of the resin sealing member 11, so that the connection reliability in the mounting step is enhanced. Besides, whether the third portions (6 c, 8 c) of the leads 6 and 8, as well as the header 7, are soldered in a satisfactory state or not can be checked visually.

The third portions (6 c, 8 c) of the leads 6 and 8 are projected from the first side face 11 z of the resin sealing member 11, and the header 7 is projected from the second side face 11 z of the resin sealing member 11. With such a structure, fillet 42 a is formed on three side faces of the third portions (6 c, 8 c) of the leads (6, 8) projecting from the first side face 11 z of the resin sealing member 11, and fillet 42 a is formed on three side faces of the header 7 projecting from the second side face 11 z of the resin sealing member 11. Consequently, the connection reliability in the mounting step is further enhanced. Moreover, whether the soldering is satisfactory or not can be checked visually.

In each power transistor 1A, as shown in FIGS. 7 and 8, the first portion 6 a of the lead 6 is exposed from the main surface 11 x of the resin sealing member 11 and is connected to the heat dissipating member 43 through a heat conducting member 44. With such a structure, heat generated from the semiconductor chip 2 is transmitted efficiently from the first portion 6 a of the lead 6 to the heat dissipating member 43 through the heat conducting member 44, so that it is possible to prevent malfunction of each power transistor 1A caused by heat and hence the reliability of the regulator 40A becomes higher.

FIG. 10 is a plan view showing a part of a lead frame which is used in manufacturing the power transistor of FIG. 1, FIGS. 11( a) and 11(b) are partially enlarged views of the lead frame of FIG. 10, in which FIG. 11( a) is a plan view and FIG. 11( b) is a sectional view taken along line a-a in FIG. 11( a), and FIG. 12 is a plan view of a header used in manufacturing the power transistor of FIG. 1.

As shown in FIGS. 10 and 11, a lead frame 20 has a plurality of product-forming areas 22 partitioned by a frame body 21 and arranged in a matrix shape. In each product-forming area 22 there are arranged two sets of leads 6 and 8 so that two products for example can be formed therein. The leads 6 and 8 are formed by bending in advance and each have a first portion (6 a or 8 a), a second portion (6 b or 8 b), and a third portion (6 c or 8 c). The leads 6 and 8 are formed integrally with the frame body 21 and the respective third portions (6 c, 8 c) are connected to the frame body 21.

The lead frame 20 is formed by etching or pressing, for example, a metallic plate formed of copper (Cu) or a copper-based alloy to form predetermined lead patterns and thereafter bending the leads.

In FIG. 11( a), the numeral 23 denotes an area where the semiconductor chip 2 is to be mounted, and numeral 24 denotes an area where the resin sealing member 11 is to be formed.

As shown in FIG. 12, the header 7 before subjected to the manufacturing process is integral with another header 7 through a connection 7 a which is to be removed in a cutting step. The number of headers 7 thus interconnected corresponds to the number of products to be obtained in each product-forming area 22. In this embodiment, two headers 7 are interconnected as an example. Each header 7 is formed, for example, by etching or pressing a metallic plate of Cu or a Cu-based alloy.

FIG. 13 is a sectional view of a semiconductor chip used in manufacturing the power transistor of FIG. 1, and FIG. 14 is a bottom view (underside view) of the semiconductor chip of FIG. 13.

As shown in FIGS. 13 and 14, a semiconductor chip 2 has a source electrode 3 and a gate electrode 4 on a main surface 2 x thereof and further has a drain electrode 4 on a back surface 2 y thereof opposite to the main surface 2 x. The drain electrode 4 is formed continuously so as to cover the back side 2 y of the semiconductor chip 2 and peripheral edges of the back side 2 y and extend toward side faces of the chip. That is, the back side 2 y of the semiconductor chip 2 and a part of side faces of the chip are covered with a conductive film which constitutes the drain electrode 4. Such a semiconductor chip 2 can be formed by carrying out dicing in two stages which dicing is for division from a state of a semiconductor wafer into a state of individual semiconductor chips. How to fabricate the semiconductor chip 2 will be described below with reference to FIGS. 15 and 16. FIG. 15 is a plan view of a semiconductor wafer used in manufacturing the power transistor of FIG. 1, and FIGS. 16( a) to 16(d) illustrate steps for dicing the semiconductor wafer into individual semiconductor chips in manufacturing the power transistor of FIG. 1, FIGS. 16( a) to 16(d) being sectional views.

First, as shown in FIGS. 15 and 16( a), a plurality of chip-forming areas 31 partitioned by dicing areas 32 are formed in a matrix shape on a main surface of a semiconductor wafer 30. The chip-forming areas 31 are each formed by forming transistor, conductive film, and insulating film.

Next, as shown in FIG. 16( b), the semiconductor wafer 30 is affixed to a dicing sheet 34 in a state in which the main surface of the semiconductor wafer 30 confronts the dicing sheet 34. Thereafter, with use of a dicing blade of a first width, the dicing areas 32 are cut from a back surface of the semiconductor wafer 32 at such a depth as does not cause separation of the chip-forming areas 31, to form grooves 33.

Next, as shown in FIG. 16( c), a conductive film 4 a such as, for example, Ti/Ni/Au film or Ti/Ni/Ag film is formed throughout the entire back surface of the semiconductor wafer 30 including the interiors of the grooves 33, thereafter, as shown in FIG. 16( d), the semiconductor wafer 30 is affixed to the dicing sheet 34 in a state in which the main surface of the semiconductor wafer confronts the dicing sheet 34, then with use of a dicing blade of a second width smaller than the first width, bottoms of the grooves 33 are cut for separation into individual chip-forming areas 31. In this way, as shown in FIG. 16( d), there are formed semiconductor chips 2 each having a drain electrode 4 which is formed continuously so as to cover not only the back surface 2 y of each semiconductor chip 2 but also a part of side faces of the chip.

Next, how to manufacture the power transistor of FIG. 1 will be described below with reference to FIGS. 17 to 24.

FIGS. 17( a) and 17(b) illustrate a manufacturing step in manufacturing the power transistor, in which FIG. 17( a) is a plan view and FIG. 17( b) is a sectional view taken along line a-a in FIG. 17( a), FIGS. 18( a) and 18(b) illustrates a manufacturing step in manufacturing the power transistor, in which FIG. 18( a) is a plan view and FIG. 18( b) is a sectional view taken along line a-a in FIG. 18( a), FIG. 19 is a partially enlarged sectional view of FIG. 18( b), FIG. 20 is a plan view illustrating a manufacturing step in manufacturing the power transistor, FIGS. 21( a) and 21(b) illustrate a manufacturing step in manufacturing the power transistor, in which FIG. 21( a) is a sectional view at a position corresponding to line a-a in FIG. 20 and FIG. 21( b) is a sectional view at a position corresponding to line b-b in FIG. 20, FIGS. 22( a) and 22(b) illustrate a manufacturing step in manufacturing the power transistor, in which FIG. 22( a) is a sectional view at a position corresponding to line a-a in FIG. 20 and FIG. 22( b) is a sectional view at a position corresponding to line b-b in FIG. 20, FIG. 23 is a plan view illustrating a manufacturing step in manufacturing the power transistor, and FIGS. 24( a) and 24(b) illustrate a manufacturing step in manufacturing the power transistor, in which FIG. 24( a) is a plan view and FIG. 24( b) is a sectional view taken along line a-a in FIG. 24( a).

First, the semiconductor chip 2 shown in FIGS. 13 and 14, the lead frame 20 shown in FIGS. 10 and 11, and the header 7 shown in FIG. 12, are provided. Though not shown, salient electrodes 9 are formed on the source electrode 3 and gate electrode 5 of the semiconductor chip 2. It is preferable that the formation of the salient electrodes 9 be done before dividing the semiconductor wafer into individual semiconductor chips 2, namely, in the stage of semiconductor wafer.

Next, the upper and lower surfaces of the lead frame 20 are inverted so that in the thickness direction of the frame body 21 there is made a change from such a state as shown in FIG. 11 wherein the first portion 6 a of the lead 6 lies in an upper position than the third portion 6 c to such a state as shown in FIG. 17 wherein the first portion 6 a of the lead 6 lies in a lower position than the third portion 6 c. Thereafter, as shown in FIG. 17, the semiconductor chip 2 is mounted on the first portions (6 a, 8 a) of the leads 6 and 8. The mounting of the semiconductor chip 2 is carried out by positioning the main surface 2 x of the semiconductor chip 2 so as to confront the firs portions (6 a, 8 a) of the leads 6 and 8 and by subsequent thermo-compression bonding. Further, the mounting of the semiconductor chip 2 is carried out in such a manner that the back surface 2 y of the semiconductor chip 2 and the third portions (6 c, 8 c) of the leads 6 and 8 are positioned on the same side.

Next, a pasty conductive adhesive (e.g., a lead-free solder paste) is applied onto the drain electrode 4 formed on the back surface 2 y of the semiconductor chip 2, then the header 7 is positioned on the drain electrode 4 through the adhesive, and subsequently the adhesive 10 is melted and cured to connect the header 7 to the drain electrode 4 electrically and mechanically.

In this step, the drain electrode 4 is formed continuously so as to cover the back surface 2 y of the semiconductor chip 2 and also a part of side faces of the chip, so that a fillet 10 a of the adhesive 10 is formed to cover a part of side faces of the semiconductor chip 2. As a result, the strength of connection between the semiconductor chip 2 and the header 7 is improved and the reliability against heat is enhanced.

Next, the upper and lower surfaces of the lead frame 20 are inverted from the state of FIG. 18 to the state of FIG. 11. Thereafter, as shown in FIG. 21, the lead frame 20 is positioned between an upper half 25 a and a lower half 25 b of a molding die 25. The positioning of the lead frame 20 is performed in the presence of an insulating sheet 27 between the lead frame 20, as well as the header 7, and the lower half 25 b. The positioning of the lead frame 20 is performed in a state in which the semiconductor chip 2, the leads (6, 8) and the header 7 are positioned in the interior of a cavity 26 formed in the molding die 25. Further, the positioning of the lead frame 20 is performed in a state in which the first portion 6 a of the lead 6 is in contact with an inner surface of the cavity 26 which confronts the first lead. In this step, the first portion 8 a of the lead 8 is smaller in thickness than the first portion 6 a of the lead 6, and an upper surface of the first portion 8 a of the lead 8 is positioned closer to the main surface 2 x of the semiconductor chip 2 than an upper surface of the first portion 6 a of the lead 6, so that a gap is formed between the first portion 8 a of the lead 8 and the inner surface of the cavity 26.

Next, a thermosetting resin is injected under pressure from a pot of the molding die 25 into the cavity 26 through a runner and a resin pouring gate to form a resin sealing member 11 as shown in FIG. 22. In this step the semiconductor chip 2 is sealed with the resin sealing member 11. The first portion 6 a of the lead 6 is exposed from a main surface 11 x of the resin sealing member 11, as shown in FIG. 23. The third portions (6 c, 8 c) of the leads 6 and 8, as well as the header 7, are exposed from the back surface 11 y of the resin sealing member 11. Further, as shown in FIG. 23, the third portions (6 c, 8 c) of the leads 6 and 8 project from a first side face 11 z of the resin sealing member 11, while the header 7 projects from a second side face 11 z of the resin sealing member.

Next, as shown in FIG. 24, the connection 7 a between two headers 7 is cut off and the third portions (6 c, 8 c) of the leads 6 and 8 are cut off from the lead frame body 21, whereby the power transistor of this first embodiment is nearly completed. The cutting of the leads 6 and 8 is performed in a projected state of the third portions (6 c, 8 c) of the leads 6 and 8 from the first side face 11 z of the resin sealing member 11.

As set forth above, the following effects are obtained by this first embodiment.

It is possible to provide a novel power transistor 1A which exhibits a high heat dissipating property and high connection reliability during mounting.

It is possible to provide a novel power transistor 1A which is high in heat dissipating property and permits visual inspection of whether soldering is good or bad at the time of mounting.

It is possible to provide a novel power transistor high in both heat dissipating property and reliability.

It is possible to provide a novel power transistor 1A high in heat dissipating property and suitable for the reduction of thickness.

It is possible to provide a novel power transistor 1A high in heat dissipating property and suitable for the reduction of size.

It is possible to provide a novel regulator 40A having a high reliability against heat.

First Modification of the First Embodiment

FIG. 25 is a sectional view of a principal portion, showing a schematic construction of a regulator according to a first modification of the first embodiment.

In a regulator 40A of this first modification, as shown in FIG. 25, for example a solder material 44 a is used as a heat conducting member, and the first portion 6 a of the lead exposed from the main surface 11 x of the resin sealing member 11 in the power transistor 1A is fixed to the heat dissipating member 43 through the solder material 44 a.

At the time of thus connecting the first portion 6 a of the lead 6 to the heat dissipating member 43 through the solder material 44 a, it is not necessary to use a mask because the first portion 8 a of the lead 8 is positioned in the interior of the resin sealing member 11. Consequently, it is possible to reduce the manufacturing cost of the regulator 40B.

Second Modification of the First Embodiment

FIGS. 26( a) and 26(b) show an internal structure of a power transistor according to a second modification of the first embodiment, in which FIG. 26( a) is a plan view and FIG. 26( b) is a sectional view taken along line a-a in FIG. 26( a).

In a power transistor 1B of this second modification, as shown in FIG. 26, slits 13 are formed through the first portion 6 a of the lead 6 so as to extend from an upper surface of the first portion 6 a to an opposite lower surface thereof. The slits 13 are formed in the other portion than the area where salient electrodes 9 are formed. In this second modification, a plurality of stripe-like slits 13 extend in X direction.

With such a concentration, it is possible to suppress a stress on bumps which stress is caused by a difference in thermal expansion coefficient between the semiconductor chip 2 and the lead 6, so that it is possible to enhance the reliability of the power transistor 1B. Particularly, since the first portion 6 a of the lead 6 is formed at as wide an area as possible for the purpose of improving the heat dissipating property, it is important that the slits 13 be formed for relaxing the stress concentrated on the salient electrodes 9.

However, since the formation of the slits 13 leads to deterioration of the heat dissipating property, it is necessary that the number and size of the slits 13 be determined taking the stress concentrated on the salient electrodes 9 and heat dissipating property into account.

Further, at the time of forming the resin sealing member 11, resin is apt to get in between the main surface of the semiconductor chip 2 and the first portion 6 a of the lead 6, so it is possible to suppress the formation of voids.

Although the slits 13 formed in this second modification extends in X direction, the extending direction of the slits 13 is not limited thereto, but slits extending for example in Y direction, or slits extending obliquely relative to X and Y directions, will also do. What is important is to form the slits 13 so as to be each positioned between adjacent salient electrodes 7. It is preferable that the number of slits 13 be determined according to the number of salient electrodes 9. As the case may be, only one slit may be formed.

Third Modification of the First Embodiment

FIGS. 27( a) and 27(b) illustrate an internal structure of a power transistor according to a third modification of the first embodiment, in which FIG. 27( a) is a plan view and FIG. 27( b) is a sectional view taken along line a-a in FIG. 27( a).

In a power transistor 1C of this third modification, grooves 14 are formed in the first portion 6 a of the lead 6. The grooves 14 are recessed from the lower surface (the surface which confronts the chip) of the first portion 6 a of the lead 6 toward the opposite upper surface thereof and are formed in the other portion than the area where bumps 9 are formed. In this third modification there are formed a plurality of stripe-like grooves 14 extending in X direction.

According to such a construction, it is possible to suppress a stress concentration on the salient electrodes 9 without causing a great deterioration of heat dissipating property. Besides, as in the previous second modification, it is possible to suppress the formation of voids.

Although the grooves 14 formed in this third modification extend in X direction, the extending direction of the grooves 14 is not limited thereto. For example, grooves extending in Y direction, or grooves extending obliquely relative to both X and Y directions, will also do. What is important is to form the grooves 14 so as to be positioned between adjacent salient electrodes 9. As to the number of grooves 14, it is preferably determined according to the number of salient electrodes 9. As the case may be, it may be unity.

Fourth Modification of the First Embodiment

FIGS. 28( a) and 28(b) illustrate an internal structure of a power transistor according to a fourth modification of the first embodiment, in which FIG. 28( a) is a plan view and FIG. 28( b) is a sectional view taken along line a-a in FIG. 28( a).

A power transistor 1D of this fourth embodiment uses an electrically conductive adhesive 15 (e.g., a solder material) as connecting means for connection between the source electrode 3 of the semiconductor chip 2 and the first portion 6 a of the lead 6. According to this construction, the amount of resin of the resin sealing member 11 interposed between the source electrode 3 of the semiconductor chip 2 and the first portion 6 a of the lead 6 becomes smaller, so that the heat dissipating property can be further enhanced.

Fifth Modification of the First Embodiment

FIGS. 29( a) and 29(b) illustrates an internal structure of a power transistor according to a fifth modification of the first embodiment, in which FIG. 29( a) is a plan view and FIG. 29( b) is a sectional view taken along line a-a in FIG. 29( a).

In a power transistor 1E of this fifth embodiment, a lead 16 is positioned outside the semiconductor chip 2 and an electric connection between the gate electrode 5 of the semiconductor chip 2 and the lead 16 is effected through a bonding wire 17.

The lead 16 is positioned on the back surface 11 y side relative to the main surface 11 x of the resin sealing member 11 and its surface side to which the wire is connected is covered with the resin of the resin sealing member 11. Like the third portion 6 c of the lead 6, the lead 16 is exposed from both back surface 11 y and first side face 11 z of the resin sealing member 11.

Also in this fifth modification there are obtained the same effects as in the first embodiment.

Sixth Modification of the First Embodiment

FIG. 30 is a plan view illustrating an internal structure of a power transistor according to a sixth modification of the first embodiment.

In a power transistor 1F of this sixth modification, slits 18 extending from the tip of the third portion 6 c of the lead 6 toward the first portion 6 a of the lead are formed in the lead 6. In this sixth modification, two such slits 18 are provided, extending from the tip of the third portion 6 c up to the first portion 6 a.

According to this construction, even if the width of the lead 6 is increased for attaining a low ON resistance and improving the heat dissipating property, it is possible to make the bending work for the lead 6 less difficult, so that it is possible to increase the productivity in the lead bending work.

Seventh Modification of the First Embodiment

FIG. 31 is a sectional view illustrating an internal structure of a power transistor according to a seventh modification of the first embodiment.

In a power transistor 1G of this seventh modification, as shown in FIG. 31, grooves 19 are formed in the first portion 6 a of the lead 6. The grooves 19 are recessed from the lower surface (the surface which confronts the chip) of the first portion 6 a of the lead 6 toward the opposite upper surface and are formed in the area to which the salient electrodes 9 are connected.

Also in this seventh modification there are obtained the same effects as in the third modification. Besides, since the height of each salient electrode 9 can be offset by each groove 19, it is possible to thin the power transistor 1G.

Second Embodiment

FIGS. 32( a) and 32(b) illustrate appearance of a power transistor according to a second embodiment of the present invention, in which FIG. 32( a) is a plan view (top view) and FIG. 32( b) is a bottom view (underside view), and FIG. 33 is a sectional view taken along line a-a in FIG. 32( a).

In a power transistor 1H of this second embodiment, as shown in FIGS. 32 and 33, a main surface 11 x of a resin sealing member 11 and a back surface 11 y thereof are approximately the same in size and shape and side faces 11 z of the resin sealing member 11 are approximately perpendicular to the main surface 11 x and back surface 11 y. Such a power transistor 1H can be formed by sealing all of plural semiconductor chips 2 with one resin sealing member and by subsequently dicing the resin sealing member, lead frame and header into individual semiconductor chips 2. Also in this case, as shown in FIGS. 32 and 33, the first portion 6 a of the lead 6 is exposed from the main surface (upper surface) 11 x of the resin sealing member 11, the third portions (6 c, 8 c) of the leads 6 and 8 are exposed from the back surface (lower surface, mounting surface) 11 y and first side face 11 z of the resin sealing member 11, and the header 7 is exposed from the back surface 11 y and second side face 11 z of the resin sealing member 11.

Also in such a power transistor 1H constructed as above of this second embodiment, the present invention is applicable and there are obtained the same effects as in the first embodiment.

Third Embodiment

FIG. 34 is a plan view (top view) showing an appearance of a power transistor according to a third embodiment of the present invention, FIG. 35 is a bottom view (underside view) showing an appearance of the power transistor of the third embodiment, FIG. 36 is an enlarged sectional view taken along line a-a in FIG. 34, and FIG. 37 is an enlarged sectional view taken along line b-b in FIG. 34.

In a power transistor 1J of this third embodiment, as shown in FIGS. 34 to 37, upper and lower surfaces of the semiconductor chip 2 are inverted. More specifically, the main surface 2 x of the semiconductor chip 2 is positioned on the back surface 11 y side of the resin sealing member 11, while the back surface 2 y of the semiconductor chip is positioned on the main surface 11 x side of the resin sealing member.

Like the lead 6 used in the first embodiment, a lead 51 is formed by bending and is provided with a first portion 51 a, a second portion 51 b, and a third portion 51 c.

The first portion 51 a of the lead 51 is connected electrically and mechanically to the drain electrode 4 on the back surface 2 y of the semiconductor chip 2 through adhesive 10 and is exposed from the main surface 11 x of the resin sealing member 11. The third portion 51 c of the lead 51 is exposed from the back surface 11 y and first side face 11 z of the resin sealing member 11.

A lead 52 is connected to the source electrode 3 on the main surface 2 x of the semiconductor chip 2 through salient electrode 9 and is exposed from the back surface 11 y and second side face 11 z of the resin sealing member 11.

A lead 53 is connected to the gate electrode 5 on the main surface 2 x of the semiconductor chip 2 through salient electrode 9 and is exposed from the back surface 11 y and second side face of the resin sealing member 11.

Also by the power transistor 1J of this third embodiment there are obtained the same effects as in the first embodiment.

Moreover, the surface side formed with source and gate regions as substantially active regions faces down and the whole surface of the chip is covered with the lead 51. This structure is strong against an external electromagnetic noises.

Fourth Embodiment

FIG. 38 is a plan view (top view) showing an appearance of a power transistor according to a fourth embodiment of the present invention, FIG. 39 is a bottom view (underside view) of the power transistor of the fourth embodiment, FIG. 40 is a plan view showing an internal structure of the power transistor of the fourth embodiment, FIG. 41 is an enlarged sectional view taken along line a-a in FIG. 40, and FIG. 42 is an enlarged sectional view taken along line b-b in FIG. 40.

As shown in FIGS. 38 to 42, a power transistor 1K of this fourth embodiment is basically of the same construction as the first embodiment and is different in the following points from the first embodiment.

A header 62 has a first portion 62 a to which the semiconductor chip 2 is adhesively fixed and a second portion 62 b formed integrally with the first portion 62 a and having a thickness greater than the first portion 62 a.

The first portion 62 a of the header 62 is exposed from the back surface 11 y of the resin sealing member 11, while the second portion 62 b of the header 62 is exposed from the main surface 11 x of the resin sealing member. Moreover, the second portion 62 b of the header 62 is exposed from the second side face 11 z of the resin sealing member 11 and is further exposed from both third and fourth side faces 11 z of the resin sealing member 11 which side faces are positioned on mutually opposite sides in Y direction.

A first portion 61 a of a lead 61 projects from the first side face 11 z of the resin sealing member 11, while a second portion 61 b and a third portion 61 c of the lead 61 are positioned outside the first side face 11 z of the resin sealing member 11.

A first portion 63 a of the lead 63 projects from the first side face 11 z of the resin sealing member 11, while a second portion 63 b and a third portion 63 c of the lead 63 are positioned outside the first side face 11 z of the resin sealing member 11.

Also by the power transistor 1K of this fourth embodiment there are obtained the same effects as in the first embodiment.

Further, since the first portion 62 a of the header 62 in this fourth embodiment is exposed from three side faces (second to fourth side faces) of the resin sealing member 11 exclusive of the first side face 11 z of the resin sealing member, so that the heat dissipating property can be further enhanced.

Fifth Embodiment

FIG. 43 is a plan view showing an internal structure of a power transistor according to a fifth embodiment of the present invention, and FIGS. 44( a) and 44(b) illustrate an internal structure of the power transistor of the fifth embodiment, in which FIG. 44( a) is a sectional view taken along line a-a in FIG. 43 and FIG. 44( b) is a sectional view taken along line b-b in FIG. 43.

A power transistor 1L of this fifth embodiment is basically of the same construction as the fourth embodiment and is different in the following points from the fourth embodiment.

As shown in FIGS. 43 and 44, the first portion 61 a and second portion 61 b of the lead 61 are positioned in the interior of the resin sealing member 11, while the third portion 61 c of the lead 61 is exposed from both back surface 11 y and first side face 11 z of the resin sealing member 11. Likewise, the first portion 63 a and second portion 63 b of the lead 63 are positioned in the interior of the resin sealing member 11, while the third portion 63 c of the lead 63 is exposed from both back surface 11 y and first side face 11 z of the resin sealing member 11.

Also by the power transistor 1L of this fifth embodiment there are obtained the same effects as in the first embodiment.

Sixth Embodiment

FIG. 45 is a plan view showing an appearance of a power transistor according to a sixth embodiment of the present invention, FIG. 46 is a bottom view showing an appearance of the power transistor of the sixth embodiment, and FIGS. 47( a) and 47(b) illustrate an internal structure of the power transistor of the sixth embodiment, in which FIG. 47( a) is a sectional view taken along line a-a n FIG. 45 and FIG. 47 (b) is a sectional view taken along line b-b in FIG. 45.

A power transistor 1M of this sixth embodiment is different from the power transistor of the previous fifth embodiment in that the upper and lower surfaces of the semiconductor chip 2 are inverted. That is, the main surface 2 x of the semiconductor chip 2 is positioned on the back surface 11 y side of the resin sealing member 11, while the back surface 2 y of the semiconductor chip is positioned on the main surface 11 x side of the resin sealing member.

The first portion 62 a of the header 62 is exposed from the main surface 11 x of the resin sealing member 11, while the second portion 62 b of the header is exposed from the back surface 11 y of the resin sealing member.

A lead 65 has a first portion 65 a and a second portion 65 b formed integrally with and thicker than the first portion 65 a. The first portion 65 a of the lead 65 is connected electrically and mechanically to the source electrode 3 on the main surface 2 x of the semiconductor chip 2 through salient electrodes 9 and is positioned in the interior of the resin sealing member 11. The second portion 65 b of the lead 65 is exposed from both back surface 11 y and first side face 11 z of the resin sealing member 11.

A lead 66 has a first portion 66 a and a second portion 66 b formed integrally with and thicker than the first portion 66 a. The first portion 66 a of the lead 66 is connected electrically and mechanically to the gate electrode 5 on the main surface 2 x of the semiconductor chip 2 through a salient electrode 9 and is positioned in the interior of the resin sealing member 11. The second portion 66 b of the lead 66 is exposed from both back surface 11 y and first side face 11 z of the resin sealing member 11.

Thus, also by the power transistor 1M of this sixth embodiment there are obtained the same effects as in the first embodiment.

Although the present invention has been described concretely by way of the above embodiments, it goes without saying that the invention is not limited to the above embodiments, but that various changes may be made within the scope not departing from the gist of the invention.

The following is a brief description of effects obtained by typical modes of the invention as disclosed herein.

It is possible to provide a novel semiconductor device high in both heat dissipating property and connection reliability in mounting.

It is possible to provide a novel semiconductor device high in heat dissipating property and permitting visual inspection of whether soldering is good or bad in mounting.

It is possible to provide a novel semiconductor device high in both heat dissipating property and reliability.

It is possible to provide a novel semiconductor device high in heat dissipating property.

It is possible to provide an electronic device high in reliability. 

The invention claimed is:
 1. A semiconductor device comprising: (a) a semiconductor chip having a quadrangular shape and having a main surface over which a first electrode pad and a second electrode pad are formed, a back surface over which a third electrode is formed opposite the main surface, a first side, a second side which intersects the first side, a third side opposite the first side, and a fourth side opposite the second side; (b) a first metal conductor having a first obverse surface, a first reverse surface opposite the first obverse surface, a first portion located over the first electrode pad of the semiconductor chip and extending in a first direction and a second direction perpendicular to the first direction, a third portion whose first reverse surface is located under the first reverse surface of the first portion in a thickness direction of the semiconductor chip, and a second portion located between the first and third portions in the first direction and interconnected with the first and third portions, wherein the first reverse surface of the first portion of the first metal conductor is electrically connected to the first electrode pad of the semiconductor chip via a first conductive adhesive, and wherein, in a plan view of the main surface of the semiconductor chip, the first portion of the first metal conductor overlaps with a part of each of the first to fourth sides: (c) a second metal conductor having a second obverse surface, a second reverse surface opposite the second obverse surface, a fourth portion located over the second electrode pad of the semiconductor chip and extending in the first direction, a sixth portion whose second reverse surface is located under the second reverse surface of the fourth portion in the thickness direction, and a fifth portion located between the fourth and sixth portions in the first direction and interconnected with the fourth and sixth portions, wherein the second reverse surface of the fourth portion is electrically connected to the second electrode pad of the semiconductor chip via a second conductive adhesive, and wherein, in the plan view, the fourth portion of the second metal conductor overlaps with a different part from the part with which the first portion of the first metal conductor overlaps of the first side and a part of the second sides and does not overlap with the third and fourth sides of the semiconductor chip; (d) a third metal conductor having a third obverse surface over which the semiconductor chip is mounted such that the back surface of the semiconductor chip faces to the third obverse surface and a third reverse surface opposite the third obverse surface, the third obverse surface being electrically connected to the third electrode of the semiconductor chip; and (e) a sealing body having a top surface and a bottom surface opposite the top surface, and sealing the semiconductor chip, the second portion of the first metal conductor, the fifth portion of the second metal conductor, and the third obverse surface of the third metal conductor, wherein a part of the first obverse surface of the first portion of the first metal conductor is exposed from the top surface of the sealing body, wherein the second obverse surface of the fourth portion of the second metal conductor is located under the first obverse surface of the first portion of the first metal conductor and sealed with the sealing body, wherein a part of each of the first reverse surface of the third portion of the first metal conductor, the second reverse surface of the sixth portion of the second metal conductor, and the third reverse surface of the third metal conductor is exposed from the bottom surface of the sealing body, and wherein, in the plan view, the second electrode pad of the semiconductor chip is located in an area provided by the first portion of the first metal conductor and the first and second sides of the semiconductor chip.
 2. The semiconductor device according to claim 1, wherein the semiconductor chip has a rectangular shape and thereby the first and second sides are short and long and short sides, respectively.
 3. The semiconductor device according to claim 1, wherein each of the first and second conductive adhesives is solder.
 4. The semiconductor device according to claim 1, wherein the first reverse surface of the third portion of the first metal conductor, the second reverse surface of the sixth portion of the second metal conductor, the third reverse surface located directly below the semiconductor chip of the third metal conductor, and the bottom surface of the sealing body are in a same plane, respectively.
 5. The semiconductor device according to claim 1, wherein, in the thickness direction, a thickness from the second obverse surface to the second reverse surface of the fourth portion of the second metal conductor is thinner than a thickness from the first obverse surface to the first reverse surface of the first portion of the first metal conductor.
 6. The semiconductor device according to claim 1, wherein, in the plan view, an area of the main surface of the semiconductor chip which overlaps with the first portion of the first metal conductor is greater than an area of the main surface of the semiconductor chip which does not overlap with the first portion of the first metal conductor.
 7. A semiconductor device comprising: (a) a semiconductor chip including a MOSFET, having a quadrangular shape and having a main surface over which a source electrode pad and a gate electrode pad electrically connected to the MOSFET are formed, a back surface over which a drain electrode electrically connected to the MOSFET is formed opposite the main surface, a first side, a second side which intersects the first side, a third side opposite the first side, and a fourth side opposite the second side; (b) a first metal conductor having a first obverse surface, a first reverse surface opposite the first obverse surface, a first portion located over the source electrode pad of the semiconductor chip and extending in a first direction and a second direction perpendicular to the first direction, a third portion whose first reverse surface is located under the first reverse surface of the first portion in a thickness direction of the semiconductor chip, and a second portion located between the first and third portions in the first direction and interconnected with the first and third portions, wherein the first reverse surface of the first portion of the first metal conductor is electrically connected to the source electrode pad of the semiconductor chip via a first conductive adhesive, and wherein in a plan view of the main surface of the semiconductor chip, the first portion of the first metal conductor overlaps with a part of each of the first to fourth sides; (c) a second metal conductor having a second obverse surface, a second reverse surface opposite the second obverse surface, a fourth portion located over the gate electrode pad of the semiconductor chip and extending in the first direction, a sixth portion whose second reverse surface is located under the second reverse surface of the fourth portion, in the thickness direction, and a fifth portion located between the fourth and sixth portions in the first direction and interconnected with the fourth and sixth portions, wherein the second reverse surface of the fourth portion is electrically connected to the gate electrode pad of the semiconductor chip via a second conductive adhesive, and wherein, in the plan view, the fourth portion of the second metal conductor overlaps with a different part from the part with which the first portion of the first metal conductor overlaps of the first side and a part of the second sides and does not overlap with the third and fourth sides of the semiconductor chip; (d) a third metal conductor having a third obverse surface over which the semiconductor chip is mounted such that the back surface of the semiconductor chip faces to the third obverse surface and a third reverse surface opposite the third obverse surface, the third obverse surface is electrically connected to the drain electrode of the semiconductor chip; and, (e) a sealing body having a top surface and a bottom surface opposite to the top surface, and sealing the semiconductor chip, the second portion of the first metal conductor, the fifth portion of the second metal conductor, and the third obverse surface of the third metal conductor, wherein a part of the first obverse surface of the first portion of the first metal conductor is exposed from the top surface of the sealing body, wherein the second obverse surface of the fourth portion of the second metal conductor is located under the first obverse surface of the first portion of the first metal conductor and sealed with the sealing body, wherein a part of each of the first reverse surface of the third portion of the first metal conductor, a part of the second reverse surface of the sixth portion of the second metal conductor, and a part of the third reverse surface of the third metal conductor is exposed from the bottom surface of the sealing body, and wherein, in the plan view, the gate electrode pad of the semiconductor chip is located in an area provided by the first portion of the first metal conductor and the first and second sides of the semiconductor chip.
 8. The semiconductor device according to claim 7, wherein the semiconductor chip has a rectangular shape and thereby the first and second sides are short and long and short sides, respectively.
 9. The semiconductor device according to claim 7, wherein each of the first and second conductive adhesives is solder.
 10. The semiconductor device according to claim 7, wherein the first reverse surface of the third portion of the first metal conductor, the second reverse surface of the sixth portion of the second metal conductor, the third reverse surface located directly below the semiconductor chip of the third metal conductor, and the bottom surface of the sealing body are in a same plane, respectively.
 11. The semiconductor device according to claim 7, wherein, in the thickness direction, a thickness from the second obverse surface to the second reverse surface of the fourth portion of the second metal conductor is thinner than a thickness from the first obverse surface to the first reverse surface of the first portion of the first metal conductor.
 12. The semiconductor device according to claim 7, wherein, in the plan view, an area of the main surface of the semiconductor chip which overlaps with the first portion of the first metal conductor is greater than an area of the main surface of the semiconductor chip which does not overlap with the first portion of the first metal conductor. 